DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to e.g. homes and small businesses over ordinary copper telephone lines. Digital Subscriber Line is a technology that assumes digital data does not have to be converted into analogue form and back. Digital data is transmitted to a subscriber directly as digital data and this allows a much wider bandwidth to be used for transmitting the data than in traditional telephone systems. Several modulation technologies are used by various kinds of DSL (such as DSL, HDSL, SDSL, ADSL, RADSL and VDSL), and these are being standardized by the International Telecommunication Union (ITU).
In a typical DSL access system configuration, subscriber devices, such as telephones or IP terminals, are connected to a DSL line via a multiplexer (also known as Integrated Access Device, IAD), which comprises a DSL modem and provides access to the DSL system. The subscriber devices and the multiplexer, i.e. terminal equipment located at the premises owned or controlled by the customer using network services are referred to as Customer Premises Equipment or CPE. The DSL line is further connected to a DSL Access Multiplexer (DSLAM), which connects a number of DSL lines to other networks, such as the Internet, typically via a backbone network, which employs e.g. Internet Protocol (IP) or IP over ATM (Asynchronous Transfer Mode).
A DSL access system further comprises an Element Management System (EMS), which provides an interface for managing the various elements of the DSL access system network. With the management system, a network operator can communicate with the network elements. A function associated with the EMS is Customer Premises Equipment Management System (CPE-MS). The CPE-MS is typically used for various monitoring, diagnosis and configuration purposes and communicates with the customer premises equipment. The communication between the CPE-MS and CPE typically employs TCP/IP protocol (Transmission Control Protocol/Internet Protocol) or UDP/IP (User Datagram Protocol) transport protocol messages. The TCP/IP acts as the data transmission protocol in the Internet, the special advantage being its independence of different device or software architectures, which makes it the most generally used network protocol in the world, especially in local networks. In Internet-based networks, the IP protocol is the actual network protocol, which serves to route an addressed IP message from a source station to a destination station.
A problem associated with the transmission of management messages between the CPE-MS and the CPE using IP is that a dedicated management IP address should be reserved for each CPE, which is impractical as the number of CPEs may be high, even hundreds. For the same reason, also the use of dedicated point-to-point connections between the CPE-MS and the CPE for management purposes is impractical.